Lubricating greases



United States Patent 3,103,493 LUBRICATING GREASES Aleksander Groszekand Geoffrey Hairsine Bell, Sunburyoil-Thames, England, assignors to TheBritish Petroleum Company Limited, London, England, a iointstockcorporation of Great Britain N0 Drawing. Filed June 24, 1960, Ser. No.38,430 Claims priority, application Great Britain July 2, 1959 18Claims. (Cl. 2S2--41) It is known to prepare lubricating greases bythickening lubricating oils with lithium hydroxy stearate. These greasesmay, in some cases, be prepared by dissolving pre-formed lithium hydroxystearate in a lubricating oil at an elevated temperature, rapidlycooling the solution and milling the gel so formed so as to convert itinto a grease. In many cases, however, this technique results in theformation of a slurry of coarse granules of soap in the oil. Anothermethod of preparing lithium hydroxy stearate greases is to saponifyhydrogenated castor oil in part or all of the oil to be thickened so asto cause the formation of lithium hydroxy stearate in situ. Althoughsomewhat more complicated than the first-mentioncd method, this methodhas the advantage that the glycerol formed during the preparation formsa complex with the soap which imparts good mechanical stability to thegrease. Again, however, the formation of a slurry of coarse granulesoften occurs when this method is used.

We have now found that the formation of lithium hydroxy steal-ategreases can be facilitated by the use of a particular type oflubricating oil base stock.

According to the invention, there is provided a lubricating grease whichhas been prepared by thickening to a grease consistency with an alkalimetal soap of a hydroxy fatty acid, e.g. an alkali metal soap of ahydrorsy stearic acid such as lithium hydroxy stearatc, a liquidpetroleum lubricating oil base stock consisting of or containing anaromatic fraction which has been separated from a petroleum lubricatingoil fraction. Preferably the grease contains 5-15% by weight of thesoap.

The liquid lubricating oil base stock may consist of a blend of thearomatic fraction and a petroleum lubricating oil fraction. Particularlysuitable blends are those containing at least by weight, e.g. l075% byweight, of the aromatic fraction. A suitable petroleum lubricating oilfraction for use in the preparation of the blends is a dewaxed vacuumdistillate, particularly a dewaxed vacuum distillate having a viscosityindex of at least 40, preferably at least 60, and preferably having aviscosity in the range 45-200 Redwood 1 seconds at 140 F.

The aromatic fraction may be prepared by selective adsorption of apetroleum lubricating oil fraction on silica gel, activated clay, orother adsorbent material. For example, the lubricating oil fraction maybe allowed to flow down a column of silica gel which is thereaftereluted with a solvent which preferentially removes from the adsorbentthat part of the oil consisting of saturated hydrocarbons. A suitablesolvent for this purpose is a low boiling saturated hydrocarbon e.g.petroleum ether, nhexane, n-heptane or iso-octane. The aromatichydrocarbons which remain in the adsorbent together with most of thesulphur-, oxygenand nitrogen-containing compounds can then be displacedfrom the adsorbent by a strongly polar, low boiling solvent e.g.acetone, ethyl alcohol, methyl alcohol, isopropyl alcohol, ethyl etheror isopropyl ether. The aromatic fraction recovered after evaporation ofthe solvent may be used by itself for the preparation of the greasesaccording to the invention, or it may be added to a lubricating oildistillate of the aforementioned type to increase the concentration ofaromatics in it.

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Another method that can be used to produce a suitable aromatic fractionis the well-known solvent extraction process. The aromatic extractsobtained by treatment of lubricating oil distillates of theaforementioned type can be used per so as the base stock or they may beadded to a lubricating oil distillate to increase its content ofaromatic hydrocarbons.

Preferably the lubricating oil base stock is one having an aromaticcontent of at least 40%, especially at least 50%, by weight asdetermined by the rapid method of silica gel chromatography described inthe Journal of the Institute of Petroleum for July 1958, volume 44,pages 212-2l5.

inspection data on several greases is given below in order to illustratethe invention. The greases were prepared from the following base oils:

Oil A.--A 160/95 grade lubricating oil (i.e. a lubricating oil having aRedwood I viscosity at F. of 160 sees, and a viscosity index of 95). OilA contained 29% by weight of aromatics.

Oil B.-A /75 grade lubricating oil containing 42% by weight ofaromatics.

Oil P.-An aromatic oil obtained from oil B by adsorption of oil B on acolumn of silica gel, elution of the saturated hydrocarbons withism-octane and recovery of the aromatic hydrocarbons by elution withisopropyl alcohol followed by evaporation of the latter. The aromaticfraction obtained in this way amounted to 41.3% by weight of theoriginal oil.

Oil D.A material extracted from a waxy petroleum vacuum distillate byi'urfural. The undissolved material obtained after this furfuralextraction and dewaxing was a lubricating oil of /95 grade. Oil D wasrecovered from solution in the furfural and had a sulphur content of5.1% by weight and an aromatic content of 87% by weight.

Oil S.--A material extracted from a waxy petroleum vacuum distillate byfurfural. The undissolvcd material obtained after the furfuralextraction and dewaxing was a lubricating oil of 65/100 grade. Oil S wasrecovered from solution in the furfural and had a sulphur content of5.78% by weight and aromatic content of about 85% by weight.

Oil T.-A material obtained by hydrofining oil D to reduce its sulphurcontent. Oil T had a sulphur content of 1.46% by weight and an aromaticcontent of 80% by weight.

Oil Q.A blend of oil A and oil D containing 75% by weight of oil A and25% by weight of oil D. Oil Q contained 44% by weight of aromatics.

Oil R.-A blend of oil A and oil D- containing 50% by weight of oil A and50% by weight of oil D. Oil R contained 58% by weight of aromatics.

Oil U.A blend of oil A and oil T containing 75% by weight of oil A and25% by weight of oil T. Oil U contained 42% by weight of aromatics.

Oil V.A blend of oil A and oil T containing 50% by weight of oil A and50% by weight of oil T. Oil U contained 55% by weight of aromatics.

OH l-V.--A blend of oil B and oil S containing 75% by weight of oil Band 25% by weight of oil S. Oil W contained 53% by weight of aromatics.

0:! X. A blend of oil B and oil S containing 50% by weight of oil B and50% by Weight of oil S. Oil W contained 63% by weight of aromatics.

The aromatic contents of oils A, B, P, Q and R were determined by therapid method of silica gel chromatography mentioned above.

EXAMPLE 1 Two greases according to the invention and two greases forcomparison were prepared using pre-forrned commercial lithium hydroxystearate and the base oils A, B and P specified above. Each of the fourgreases was formed by dissolving the soap in the oil at 225 C., pouringthe solution into a cooled tray and milling the gel W and X are ofbetter consistency than the correspond ing comparative grease B2.

We claim:

1. A lubricating grease consisting essentially of a petroso formed in aroller mill at 0.005 inch ga The 'soap 5 leurn lubricating oil basestock and a thickening agent, contents and various inspection data onthese four greases in which the thickening agent is an alkali metal soapof are given in Table l, in which greases P1 and P2 are asoap-forminghydroxy fatty acid and the petroleum lubrigreases according to theinvention and greases A1 and eating oil base stock contains at least 40%by weight B1 are greases prepared for comparison. of an aromaticfraction which has been separated from Table 1 a petroleum lubricatingoil fraction.

2. A lubricating grease according to claim 1, in which the soap is analkali metal hydroxy stearate. m iff ala 3. A lubricating greaseaccording to claim 2, in which the soap is a lithium hydroxy stearate.Base unused on A O B on ml 4. A lubricating grease according to claim 1,in which Content or mmtiiics in the base oil, 42 :00 100 the base stockhas been prepared by blending a petroleum sdil p c iii i ezli i'mtion,13 lubricating oil fraction and an aromatic fraction which Penetration11 50 or has been separated during the preparation of a petroleum g fgfk I lubricating oil fraction. 100,000 Sll'0 kCS 20 5. A lubricatinggrease according to claim 4, in which l l ele d fl sl fll Tlylmgpcrccntwt III: 1 3 at least one of the petroleum lubricating oil fractions wasa dewaxed vacuum distillate. 1 Semmquid Slurry. 6. A. lubricating greaseaccording to claim 5, in which It will be Seen that the greasesaccording to the gheledlestviiged vacuum distillate had a viscosityindex of vention (greases P1 and P2) are of good consist n y 7 Alubrlating grease according to claim 6, in which even though smallersoap concentrations than usual were the dewaxed vacuum distillate had aviscosity index of employed. Grease P1 which has a smaller soap conatleast 60 cenlratlon than B1 very.much l i pene' 8. A lubricating greaseaccording to claim 5, in which tration. Grease P2 is comparable inpenetration and p the viscosity of the dewaxed vacuum distillate was instability With grease B1 although its soap contentiation the range of200 Redwood I seconds at 140 F. is very much less. G1 ease P2 also has asatisfactory drop oint and gives a satisfactor p rformarm: in the bleedA lubncatmg grease accordmg to Clalm m whlch y w the base stock contains40-75% by weight of the aromatic fraction.

EXAMPLE I 35 10. A lubricating grease according to claim 1, in whichNine greases were prepared to illustrate the propertles the aromaticfraction was obtained by solvent extraction. of greases prepared fromhydrogenated castor oil by 11. A lubricating grease according to claim1, in which saponification in situ. Greases prepared by this techthearomatic fraction was obtained by a chromatographic nique containglycerol produced from the hydrogenated process, castor oil. Each samplewas prepared by dissolving 13 4U 12. A lubricating grease according toclaim 10, in which by weight of hydrogenated castor oil in a lubricatingoil the chromatographic process comprised adsorption of base stock at100 C. Aqueous lithium hydroxide soluthe petroleum lubricating oilfraction on an adsorbent mation was added to saponify the hydrogenatedCastor oil terial, elution of at least some of the aliphatic materialsand the temperature raised to 170 C. to rcniiwc the with a solvent andrecovery of the aromatic fraction.

Table 2 Grease Number I A2 Q l R A3 1 U l V B2 W X Base on Used 011A ono 011R OilA Oil U 011V Oil B on W OilX Content otarornatics in the baseoil, percent Wt .u 2!] 44 58 29 42 42 53 63 Soap Concentration, percentwti 13 13 13 13 13 13 13 13 13 Penetration (IP50):

Unworked 253 215 102 250 225 214 239 220 10s 00 Str0kes 266 222 100 20?243 232 220 210 205 100,000 Str0kcs 30a 2112 275 203 251 200 Drop Point(IP31), 186 us 150 100 103 188 100 189 is? Bleed Test (DTD 825), percentwt 4.3 0.2 Nil Nil Nil Nil Nil Nil Nil final traces of water. Themixture was agitated during 13. Alubricating grease according to claim12, in which saponification and dehydration and stirring was continuedthe lubricating oil was adsorbed on an adsorbent selected until thetemperature had fallen to below 100 C. When from the group consisting ofsilica gel and activated clay. room temperature had been reached thegrease was milled 14. A lubricating grease according to claim 12, inwhich on a roller mill at a 0.005 inch gap and deaeratcd. the solventused to elute the aliphatic materials was one The compositions andvarious inspection data of the selected from the group consisting ofpetroleum ether, nine greases prepared by the method outlined abov are-1 d i t given i Tab 2 in WhiCh greases Q W and X 15. A lubricatinggrease according to claim 12, in which are greases according to theinvention and gr ases A the aromatic fraction was recovered by elutionwith a A3 and B2 are greases prepared for comparison. solvent selectedfrom the group consisting of acetone, It will be seen that greases Q, R,U and V, particularly ethyl alcohol, methyl alcohol, isopropyl alcohol,ethyl greases R, have lower penetrations than the correspondether andisopropyl ether. ing comparative greases A2 and A3. Similarly greases16. A lubricating grease according to claim 1, in which 5 6 the aromaticcontent of the lubricating oil base stock 18. A lubricating greaseaccording to claim 1, which is at least 50% by weight. contains 545% byweight of soap.

17. A lubricating grease according to claim 1, in which the soap wasprepared by the saponification in aim of References Cited in the file ofthis patent hydrogenated caster Oil. 5 UNITED STATES PATENTS 2,625,510Moore Ian. 13, 1953

1. A LUBRICATING GREASE CONTAINING ESSENTIALLY OF A PETROLEUMLUBRICATING OIL BASE STOCK AND A THICKENING AGENT, IN WHICH THETHICKENING AGENT IS AN ALKALI METAL SOAP OF A SOAP-FORMING HYDROXY FATTYACID AND THE PETROLEUM LUBRICATING OIL BASE STOCK CONTAINS AT LEAST 40%BY WEIGHT OF AN AROMATIC FRACTION WHICH HAS BEEN SEPARATED FROM APETROLEUM LUBRICATING OIL FRACTION.